The present invention relates to a new and distinctive soybean cultivar, designated 921021. There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, resistance to diseases and insects, better stems and roots, tolerance to drought and heat, and better agronomic quality.
Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F1 hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; those still deficient in a few traits may be used as parents to produce new populations for further selection.
These processes, which lead to the final step of marketing and distribution, usually take from eight to 12 years from the time the first cross is made. Therefore, development of new cultivars is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard cultivar. If a single observation is inconclusive, replicated observations provide a better estimate of its genetic worth.
The goal of plant breeding is to develop new, unique and superior soybean cultivars and hybrids. The breeder initially selects and crosses two or more parental lines, followed by repeated selfing and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop the same line, or even very similar lines, having the same soybean traits.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made, during and at the end of the growing season. The cultivars which are developed are unpredictable. This unpredictability is because the breeder""s selection occurs in unique environments, with no control at the DNA level (using conventional breeding procedures), and with millions of different possible genetic combinations being generated. A breeder of ordinary skill in the art cannot predict the final resulting lines he develops, except possibly in a very gross and general fashion. The same breeder cannot produce the same cultivar twice by using the exact same original parents and the same selection techniques. This unpredictability results in the expenditure of large amounts of research monies to develop superior new soybean cultivars.
The development of new soybean cultivars requires the development and selection of soybean varieties, the crossing of these varieties and selection of superior hybrid crosses. The hybrid seed is produced by manual crosses between selected male-fertile parents or by using male sterility systems. These hybrids are selected for certain single gene traits such as pod color, flower color, pubescence color or herbicide resistance which indicate that the seed is truly a hybrid. Additional data on parental lines, as well as the phenotype of the hybrid, influence the breeder""s decision whether to continue with the specific hybrid cross.
Pedigree breeding and recurrent selection breeding methods are used to develop cultivars from breeding populations. Breeding programs combine desirable traits from two or more cultivars or various broad-based sources into breeding pools from which cultivars are developed by selfing and selection of desired phenotypes. The new cultivars are evaluated to determine which have commercial potential.
Pedigree breeding is used commonly for the improvement of self-pollinating crops. Two parents which possess favorable, complementary traits are crossed to produce an F1. An F2 population is produced by selfing one or several F1""s. Selection of the best individuals may begin in the F2 population; then, beginning in the F3, the best individuals in the best families are selected. Replicated testing of families can begin in the F4 generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F6 and F7), the best lines or mixtures of phenotypically similar lines are tested for potential release as new cultivars.
Mass and recurrent selections can be used to improve populations of either self- or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line which is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent.
The single-seed descent procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one-seed sample to plant the next generation. When the population has been advanced from the F2 to the desired level of inbreeding, the plants from which lines are derived will each trace to different F2 individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F2 plants originally sampled in the population will be represented by a progeny when generation advance is completed.
In a multiple-seed procedure, soybean breeders commonly harvest one or more pods from each plant in a population and thresh them together to form a bulk. Part of the bulk is used to plant the next generation and part is put in reserve. The procedure has been referred to as modified single-seed descent or the pod-bulk technique.
The multiple-seed procedure has been used to save labor at harvest. It is considerably faster to thresh pods with a machine than to remove one seed from each by hand for the single-seed procedure. The multiple-seed procedure also makes it possible to plant the same number of seeds of a population each generation of inbreeding. Enough seeds are harvested to make up for those plants that did not germinate or produce seed.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987).
Proper testing should detect any major faults and establish the level of superiority or improvement over current cultivars. In addition to showing superior performance, there must be a demand for a new cultivar that is compatible with industry standards or which creates a new market. The introduction of a new cultivar will incur additional costs to the seed producer, the grower, processor and consumer; for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing preceding release of a new cultivar should take into consideration research and development costs as well as technical superiority of the final cultivar. For seed-propagated cultivars, it must be feasible to produce seed easily and economically.
Soybean, Glycine max (L), is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop stable, high yielding soybean cultivars that are agronomically sound. The reasons for this goal are obviously to maximize the amount of grain produced on the land used and to supply food for both animals and humans. To accomplish this goal, the soybean breeder must select and develop soybean plants that have the traits that result in superior cultivars.
According to the invention, there is provided a novel soybean cultivar, designated 921021. This invention thus relates to the seeds of soybean cultivar 921021, to the plants of soybean 921021 and to methods for producing a soybean plant produced by crossing the soybean 921021 with itself or another soybean line, and the creation of variants by mutagenesis or transformation of soybean 921021.
Thus, any such methods using the soybean variety 921021 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using soybean variety 921021 as a parent are within the scope of this invention. Advantageously, the soybean variety could be used in crosses with other, different, soybean plants to produce first generation (F1) soybean hybrid seeds and plants with superior characteristics.
In another aspect, the present invention provides for single or multiple gene converted plants of 921021. The transferred gene(s) may preferably be a dominant or recessive allele. Preferably, the transferred gene(s) will confer such traits as herbicide resistance, insect resistance, resistance for bacterial, fungal, or viral disease, male fertility, male sterility, enhanced nutritional quality, and industrial usage. The gene may be a naturally occurring soybean gene or a transgene introduced through genetic engineering techniques.
In another aspect, the present invention provides regenerable cells for use in tissue culture of soybean plant 921021. The tissue culture will preferably be capable of regenerating plants having the physiological and morphological characteristics of the foregoing soybean plant, and of regenerating plants having substantially the same genotype as the foregoing soybean plant. Preferably, the regenerable cells in such tissue cultures will be embryos, protoplasts, meristematic cells, callus, pollen, leaves, anthers, roots, root tips, flowers, seeds, pods or stems. Still further, the present invention provides soybean plants regenerated from the tissue cultures of the invention.
In the description and tables which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided:
Allele. Allele is any of one or more alternative forms of a gene, all of which alleles relate to one trait or characteristic. In a diploid cell or organism, the two alleles of a given gene occupy corresponding loci on a pair of homologous chromosomes.
Backcrossing. Backcrossing is a process in which a breeder repeatedly crosses hybrid progeny back to one of the parents, for example, a first generation hybrid F. with one of the parental genotypes of the F1 hybrid.
Brown Stem Rot. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based on leaf symptoms of yellowing and necrosis caused by brown stem rot. A score of 9 indicates no symptoms. Visual scores range to a score of 1 which indicates severe symptoms of leaf yellowing and necrosis.
Cotyledon. A cotyledon is a type of seed leaf. The cotyledon contains the food storage tissues of the seed.
Embryo. The embryo is the small plant contained within a mature seed.
Emergence. This score indicates the ability of the seed to emerge when planted 3xe2x80x3 deep in sand and with a controlled temperature of 25xc2x0 C. The number of plants that emerge each day are counted. Based on this data, each genotype is given a 1 to 9 score based on its rate of emergence and percent of emergence. A score of 9 indicates an excellent rate and percent of emergence, an intermediate score of 5 indicates average ratings and a 1 score indicates a very poor rate and percent of emergence.
Hilum. This refers to the scar left on the seed which marks the place where the seed was attached to the pod prior to the seed being harvested.
Hypocotyl. A hypocotyl is the portion of an embryo or seedling between the cotyledons and the root. Therefore, it can be considered a transition zone between shoot and root.
Iron-Deficiency Chlorosis. Plants are scored 1 to 9 based on visual observations. A score of 9 means no stunting of the plants or yellowing of the leaves and a score of 1 indicates the plants are dead or dying caused by iron-deficiency chlorosis, a score of 5 means plants have intermediate health with some leaf yellowing.
Lodging Resistance. Lodging is rated on a scale of 1 to 9. A score of 9 indicates erect plants. A score of 5 indicates plants are leaning at a 45xc2x0 angle in relation to the ground and a score of 1 indicates plants are laying on the ground.
Maturity Date. Plants are considered mature when 95% of the pods have reached their mature color. The number of days are either calculated from August 31 or from the planting date.
Maturity Group. This refers to an agreed-on industry division of groups of varieties, based on zones in which they are adapted primarily according to day length or latitude. They consist of very long day length varieties (Groups 000, 00, 0), and extend to very short day length varieties (Groups VII, VIII, IX, X).
Oil or oil percent. Soybean seeds contain a considerable amount of oil. Oil is measured by NIR spectrophotometry, and is reported on an as is percentage basis.
Oleic Acid Percent. Oleic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
Palmitic Acid Percent. Palmitic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
Phytophthora Tolerance. Tolerance to Phytophthora root rot is rated on a scale of 1 to 9, with a score of 9 being the best or highest tolerance ranging down to a score of 1 which indicates the plants have no tolerance to Phytophthora.
Phenotypic Score. The Phenotypic Score is a visual rating of general appearance of the variety. All visual traits are considered in the score including healthiness, standability, appearance and freedom of disease. Ratings are scored from 1 being poor to 9 being excellent.
Plant Height. Plant height is taken from the top of soil to top node of the plant and is measured in inches.
Pod. This refers to the fruit of a soybean plant. It consists of the hull or shell (pericarp) and the soybean seeds.
Protein Percent. Soybean seeds contain a considerable amount of protein. Protein is generally measured by NIR spectrophotometry, and is reported on an as is percentage basis.
Pubescence. This refers to a covering of very fine hairs closely arranged on the leaves, stems and pods of the soybean plant.
Quantitative Trait Loci (QTL). Quantitative trait loci (QTL) refer to genetic loci that control to some degree numerically representable traits that are usually continuously distributed.
Regeneration. Regeneration refers to the development of a plant from tissue culture.
Seed Protein Peroxidase Activity. Seed protein peroxidase activity is defined as a chemical taxonomic technique to separate cultivars based on the presence or absence of the peroxidase enzyme in the seed coat. There are two types of soybean cultivars, those having high peroxidase activity (dark red color) and those having low peroxidase activity (no color).
Seed Yield (Bushels/Acre). The yield in bushels/acre is the actual yield of the grain at harvest.
Seeds per Pound. Soybean seeds vary in seed size, therefore, the number of seeds required to make up one pound also varies. This affects the pounds of seed required to plant a given area, and can also impact end uses.
Shattering. The amount of pod dehiscence prior to harvest. Pod dehiscence involves seeds falling from the pods to the soil. This is a visual score from 1 to 9 comparing all genotypes within a given test. A score of 9 means pods have not opened and no seeds have fallen out. A score of 5 indicates approximately 50% of the pods have opened, with seeds falling to the ground and a score of 1 indicates 100% of the pods are opened.
Single Gene Converted (Conversion). Single gene converted (conversion) plant refers to plants which are developed by a plant breeding technique called backcrossing wherein essentially all of the desired morphological and physiological characteristics of a variety are recovered in addition to the single gene transferred into the variety via the backcrossing technique or via genetic engineering.